Throughout the evolution of integrated circuits, an objective of device scaling has been to increase circuit performance and to increase the functional complexity of the circuits as efficiently as possible. Additionally, as larger demands have been placed on today's integrated circuits, it has become highly desirable to integrate various electrical components into the overall circuit design.
One such electrical device that has been recently integrated into the circuit design is the metal oxide metal (MOM) capacitor. Typically, as indicated by the name, a MOM capacitor consists of a first metal electrode covered by an oxide layer, which is, in turn, covered by a second metal electrode. While the MOM capacitor's incorporation into integrated circuit design has been widely accepted, its incorporation has brought certain problems into the fabrication process, such as contamination problems, metal diffusion into the oxide and multiple processing steps that are required to achieve the desired structure.
During the MOM capacitor's production, a different machine is required to deposit each of the capacitor's layers. The first metal electrode is formed in one or more deposition chambers of a metal deposition machine by depositing a metal stack (commonly Ti/TiN) on a substrate (typically silicon), which is then subjected to a temperature sufficient to form a metal silicide interface between the substrate, which typically contains silicon, and the metal layer. After forming the first metal electrode, the partially constructed device is removed from the metal deposition chamber and moved to another chamber having an oxide deposition chamber where the oxide layer of the MOM capacitor is deposited. Next, the apparatus is then returned a metal deposition machine to form the second metal electrode of the capacitor.
By requiring multiple steps and multiple machines to complete the capacitor fabrication, the chances of exposure to numerous contaminants and possible misprocessing steps is substantially increased. Over time and after fabricating multiple lots of devices, contaminants from previous lots tend to remain within the various chambers, constituting risks to later lots placed within the same chamber. Previously, small concentrations of contaminants did not pose serious problems for manufacturers when the semiconductor structures were rather large. Unfortunately, with semiconductor dimensions rapidly shrinking, contaminants, which once were not a chief concern, now pose a strong possibility of limiting yield and reduced revenue from product. In response, manufacturers now seek ways of reducing the exposure of semiconductor devices to contaminants during production. In light of these risks, manufacturers constantly seek ways to reduce the risk of contamination of their devices and misprocessing steps.
Another problem associated with conventional processes is metal diffusion into the oxide, which can cause leakage or malfunction within the capacitor. As previously mentioned, the oxide is deposited in a different machine than one in which the metal electrode is deposited. As such, the oxide is typically very different from the metal. For example, the metal electrode may be titanium and the oxide may be silicon dioxide. In such instances, the titanium may diffuse into the silicon dioxide, which may lead to the previously mentioned problems.
Also, as discussed above, the present conventional processes require multiple steps and multiple tools, which may result in misprocessing the wrong recipe, etc. The metal is deposited in one tool and the oxide is deposited in another. Because of the extra steps required to move the wafer from one tool to another, these multiple steps are costly in both time and money and are, therefore, inefficient.
Accordingly, what is needed in the art is method that addresses the deficiencies associated with the present conventional processes discussed above.